1. Field of the Invention
The present invention relates generally to a data storage device capable of storing data provided from an external device and to a method of driving the data storage device and, more particularly, the present invention relates to a data storage device having heterogeneous types of nonvolatile memory and to a method of driving the data storage device.
2. Description of the Related Art
A data storage device generally accesses memory in response to an externally input data access command, and then stores data into or reads data from the accessed memory. The memory of the data storage device may be implemented using nonvolatile memory in which case stored data is maintained even in the absence of externally supplied power.
Nonvolatile memory types may be classified as either high-speed nonvolatile memory or low-speed nonvolatile memory. Generally, high-speed nonvolatile memory has a greater data access speed than low-speed nonvolatile memory. Each has certain advantages and disadvantages relative to the other. For example, NAND flash memory, which is an example of low-speed nonvolatile memory, can be advantageously implemented to have a high memory capacity and is relatively inexpensive to produce, but it also exhibits a relatively low data access speed.
Examples of high-speed nonvolatile memories are Ferroelectric Random Access Memory (FRAM) and Phase-change RAM (PRAM). Since high-speed nonvolatile memory, such as FRAM, more randomly accesses data, its data access speed is 1,000 times faster than that of NAND flash memory. However, it is relatively difficult to implement high-speed nonvolatile memory such as FRAM with a high memory capacity, and the manufacturing cost of such a memory is relatively high.
In the meantime, data may be generally classified as either “user data” or “metadata”. User data is data that is generated by a user, whereas metadata is data indicative of attributes of the externally input data, for example, the storage location of data as in a File Allocation Table (FAT). User data is accessed in large data quantities during each memory operation, but the access frequency is relatively small. In contrast, metadata is typically accessed in small data quantities, but with a high access frequency.
FIG. 1 is a block diagram illustrating a conventional nonvolatile data storage device 10 which receives data DTA from and supplies data DTA to an external device 20. Referring to FIG. 1, the conventional data storage device 10 includes memory controller 11 which accesses a homogeneous nonvolatile memory 12, for example, a NAND flash memory. Controls signals CON are generated by the memory controller 11 to control access to selected portions of the nonvolatile memory 12 so as to store data DTA into or retrieve data DTA from the nonvolatile memory 12. The data DTA is temporarily stored in a buffer circuit 13, and an interface circuit 14 is operatively interposed between the buffer circuit 13 and the external device 20.